Bistrifluoromethylbenzylamines and, in particular, 3,5-bistrifluoromethylbenzylamine are important as crop-protection and pharmaceutical active ingredients and as precursors therefor.
Earlier literature (see J. A. C. S. 66, 725 (1944) and 82, 2386 (1960)) and Chem. Ber. 85, 325 (1952) describe how aliphatic nitriles and indolylacetonitriles can be converted into the corresponding amines by catalytic reduction with hydrogen in the presence of Raney nickel or rhodium. If any solvents at all are used, these are alcohols. If necessary, it is possible to carry out the process in the presence of ammonia.
For the preparation of trifluoromethylbenzylamines, the catalytic reduction of trifluoromethylbenzonitriles in the presence of rhodium or palladium catalysts, ethanol and hydrogen chloride is described, where the amines are produced as hydrochloride. These hydrochlorides must be purified in a complex manner and then be converted into the free amines (see J. Pharm. Sci. 54, 1204 (1965)).
According to U.S. Pat. No. 3,726,969, the last-named process is also used for the preparation of 3,5-bistrifluoromethyl-benzylamine. Here too, complex purification steps have to be undertaken. According to this process, only the amine hydrochloride, and not the free amine, has been prepared.
There is therefore still a need for a process for the preparation of bistrifluoromethylbenzylamines in which the free amines are obtained in high purities in a simple manner.